He called himself an environmentalist and said he respects women's rights, adding that the Democratic Party "is much more embracing to those ideas."
Republicans were quick to pounce on his recent change of party.
"We are definitely looking forward to watching political opportunist Michael Parrish tie himself in knots trying to defend Obamacare and other Democratic economic policies," said Ian Prior, a spokesman for the GOP congressional campaign arm.
Though no other candidates have announced, Republican Ryan Costello, chair of Chester County's commissioners, is expected to do so this week.
Montgomery County Commissioner Leslie Richards said Monday that she would not run.
Parrish, who is chief executive at Daleco Resources, a mineral, oil, and gas company with offices in West Chester, said he decided to run after growing angry at the recent government shutdown. "My father always told us to put up or shut up," he said.
He plans to launch his campaign by releasing a Web video.
Parrish has degrees from West Point, Stanford University's aeronautical school, and the Wharton School. He flew Army helicopters during the Cold War, he said, and was an operations officer in Iraq during Desert Storm.
He said small businesses should be freed from some of the reporting requirements under the Sarbanes-Oxley law and emphasized the importance of scholarships.
"The military invested in me because they understand education is the key to innovation," he said. "The same holds true for our economy."
He said he would oppose new restrictions on abortion and favors a path to citizenship for illegal immigrants already in the United States.
"This country has grown on immigration," he said.
Parrish is a gun owner who supports expanded background checks and an assault-weapons ban. "It's important to have the freedom of gun ownership, but responsible gun ownership is critical," he said.